my 0.02$
here's how it works (from my understanding, i've filed the FAFSA 4 times for undergrad):
fill out all the info, including your parents'. as a grad student, everyone's EFC will be 0 unless you have huge assets in your name, or business, or already make a lot of $$$. thus, you will be qualified for the subsidized 8500$ loan that everyone gets. then, each school calculates their own EFC using an "in-house" formula and using the CSS profile (and any other extra forms from specific schools). obviously, the private schools with a lot of $$ take EFC into serious consideration and if it's low enough you could either get GRANT money from the school (in addition to the federal loans) and/or get school subsidized loans that are of lower interest than just regular unsubsidized loans. so, your loans will not incur interest while in school and after that it's usually ~5% fixed interest (these are the school loans). on the other hand, if it's your state school that doesn't have any $$ to give out for free based on your family's EFC (parent info), then they'll just give you loans. so your parents' info won't hurt. finally, regarding scholarships, if schools have "NEED BASED" scholarships, then there's almost no way they'd give you such a scholarship if you don't include your parents' info. otherwise, everyone would have an EFC of 0 and we're all needy.